Magnetic field concentrator for electromagnetic forming

ABSTRACT

A magnetic forming system ( 10 ) for creating a fluid circuit joint between a tube and a fitting includes an induction coil ( 12 ). The induction coil ( 12 ) may form a first stage electromagnetic current. A field concentrator ( 132 ) may focus the first stage electromagnetic current to form a second stage electromagnetic current. An insert ( 136 ) may focus the second stage electromagnetic current to form an electromagnetic field. The electromagnetic field forms the fluid circuit joint. The induction coil ( 12 ) may be insertable within the tube, generate an electromagnetic field, and impose the electromagnetic field on and to expand a portion of the tube within the fitting to form the fluid circuit joint. The system ( 10 ) may include a receptacle ( 54 ) that is external to the tube and the fitting. An insert ( 56 ) may be mechanically coupled within the receptacle ( 54 ) and limit the outward expansion of the tube and the fitting.

RELATED APPLICATION

The present invention is related to U.S. patent application Ser. No.11/028,093 entitled “Electromagnetic Mechanical Pulse Forming of FluidJoints for Low-Pressure Applications”, U.S. patent application Ser. No.11/865,452 entitled “Electromagnetic Pulse Welding of Fluid Joints”, andU.S. patent application Ser. No. 10/905,211 entitled “ElectromagneticMechanical Pulse Forming of Fluid Joints for High-PressureApplications”, which are incorporated by reference herein.

TECHNICAL FIELD

The present invention generally relates to the solid state coupling ofmetallic tubes and fittings. More specifically, the present invention isrelated to the systems and components utilized in the magnetic couplingof the tubes to the fittings.

BACKGROUND ART

Metallic tubes are commonly used to carry fluid in the form of gas orliquid throughout various fluid circuits in many industries. This isespecially true in the aerospace industry, due to the lightweight andstrong mechanical features of the metallic tubes. For example,thin-walled aluminum and stainless steel tubing is often utilized withinan aircraft to carry oxygen and hydraulic fluid for variousapplications, such as to breathing apparatuses and to and from vehiclebrakes.

The fluid circuits typically contain a vast number of interlock joints,which reside between the tubing and the end fittings, such as ferrules.The current technique used to join the different sized tubes andferrules, is referred to as a roller swaging process. During thisprocess, a tube is inserted into a ferrule while the ferrule isconstrained using a clamp. The tube is then expanded into the ferruleusing a roller. The inner walls of the ferrule typically contain grooveswithin which the tube is expanded. An interlock is created between thetube and the ferrule due to the expansion and deformation of the tubeagainst the inner walls and into the grooves of the ferrule.

Another technique that is commonly used to join metallic tubes to endfittings is referred to as Gas Tungsten Arc Welding (GTAW), which is afusion welding process. The formed joints produced from fusion weldingare often rejected by penetrant inspection, x-ray inspection, orpressure testing, and must be weld repaired. A weld formed joint mayneed to be repaired as many as three times, at significant costs.

A desire exists to increase the operating lifetime of a mechanical orfluid tight joint. Thus, there exists a need for an improved techniquefor forming a leak tight joint between a tube and a ferrule for variousfluid circuit applications. It is desirable that the improved techniquebe economical, have an associated quick production set-up time, andaccount for different sized tube and ferrule combinations.

SUMMARY OF THE INVENTION

The present invention satisfies the above-stated desires and provides aleak tight joint utilizing magnetic interactions and interchangeableinserts and nests as part of the fabrication process.

Several embodiments of the present invention provide a magnetic formingsystem for creating a fluid circuit joint between a tube and a fitting.The system includes an induction coil that forms a first stageelectromagnetic current. A field concentrator is electrically coupled tothe induction coil and focuses the first stage electromagnetic currentto form a second stage electromagnetic current. An insert iselectrically coupled to the field concentrator and focuses the secondstage electromagnetic current to form an electromagnetic field. Theelectromagnetic field forms the fluid circuit joint. The electromagneticfield is imposed to compress the fitting onto the tube, to expand thetube within the fitting, or to compress the tube onto the fitting.

Another embodiment of the present invention provides a magnetic formingsystem for creating a fluid circuit joint between a tube and a fitting.The system includes a receptacle that is external to the tube and thefitting. An insert is mechanically coupled within the receptacle andlimits the outward expansion of the tube and the fitting. An inductioncoil is insertable within the tube, generates an electromagnetic field,and imposes the electromagnetic field on and to expand a portion of thetube within the fitting to form the fluid circuit joint.

The embodiments of the present invention provide several advantages. Onesuch advantage is the provision of an economical technique to utilize afixed electromagnetic coil and a fixed magnetic field concentrator withinterchangeable inserts to allow production of a wide variety of tubeand ferrule diameters. The field concentrator features a large internaldiameter, into which a split cylindrical concentrator insert is placedto accommodate a specific tube and end fitting shape. Differentconcentrator inserts can quickly and easily be exchanged to alterproduction set-up to a different size tube and fitting.

The use of a concentrator in combination with an insert, as describedherein, reduces costs by allowing one to change over a small relativelylightweight insert while maintaining a common fixed concentrator.

The present invention itself, together with further objects andattendant advantages, will be best understood by reference to thefollowing detailed description, taken in conjunction with theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagrammatic view of a magnetic forming system inaccordance with an embodiment of the present invention.

FIG. 2A is a cross-sectional side view of a insert/nest assembly thatmay be incorporated into the system of FIG. 1 in accordance with anembodiment of the present invention.

FIG. 2B is a front half cross-sectional view of the insert/nest assemblyof FIG. 2A.

FIG. 3A is a cross-sectional side view of a insert/nest assembly thatmay be incorporated into the system of FIG. 1 in accordance with anotherembodiment of the present invention.

FIG. 3B is a front half cross-sectional view of the concentrator/nestassembly of FIG. 3A.

FIG. 4A is a cross-sectional side view of a insert /nest assembly thatmay be incorporated into the system of FIG. 1 in accordance with stillanother embodiment of the present invention.

FIG. 4B is a front half cross-sectional view of the concentrator/nestassembly of FIG. 4A.

FIG. 5 is a side cut-away view of a tube/fitting coupling incorporatinga tube/fitting joint formed using the assemblies of FIG. 2A or 3A.

FIG. 6A is a half-side cross-sectional view of a tube/fitting couplingincorporating a tube/fitting joint prior and subsequent to magneticformation using the assembly of FIG. 4A.

FIG. 6B is a side cut-away view of a tube/fitting coupling incorporatinga tube/fitting joint subsequent to magnetic formation using the assemblyof FIG. 4A.

FIG. 6C is a side cut-away view of a tube/fitting coupling subsequent tometallurgical formation using the assembly of FIG. 4A.

FIG. 7 is a cross-sectional side view of a sample fluid carrying ferrulein accordance with an embodiment of the present invention.

FIG. 8 is a cross-sectional side view of a sample hydraulic fluidcarrying ferrule in accordance with an embodiment of the presentinvention.

FIG. 9 is a cross-sectional side view of another sample hydraulic fluidcarrying ferrule in accordance with another embodiment of the presentinvention.

FIG. 10 is a first sample method of magnetically forming a fluid jointin accordance with an embodiment of the present invention.

FIG. 11 is a second sample method of magnetically forming a fluid jointin accordance with another embodiment of the present invention.

FIG. 12 is a third sample method of magnetically forming a fluid jointin accordance with still another embodiment of the present invention.

DETAILED DESCRIPTION

In each of the following Figures, the same reference numerals are usedto refer to the same components. While the present invention isdescribed with respect to a system for magnetically forming a fluidjoint and to the joints formed therefrom, the present invention may beadapted for various applications, such as air, liquid, and fluidapplications. The present invention may be applied to both low-pressureapplications, i.e. less than approximately 2500 psi, and high-pressureapplications of greater than approximately 5000 psi, as well as toapplications therebetween. The present invention may be applied to fluidapplications in the aerospace, automotive, railway, and nautical orwatercraft industries, as well as to other industries where fluid tightjoints are utilized, such as residential or commercial plumbing.

In the following description, various operating parameters andcomponents are described for one constructed embodiment. These specificparameters and components are included as examples and are not meant tobe limiting.

Also, in the following description the term “fitting” may refer to aferrule, a nut, a union, or other fitting known in the art. A fittingmay be magnetically formed or magnetically welded to or with a tubularconduit, as is described below.

Referring now to FIG. 1, a block diagrammatic view of a magnetic formingsystem 10 in accordance with an embodiment of the present invention isshown. The magnetic forming system 10 includes an induction coil 12 thatis utilized to magnetically form a fluid joint between fluid carryingtubes and fittings, some examples of fluid joints, fluid carrying tubes,and fittings are shown in FIGS. 2A-9.

In operation, the induction coil 12 receives current generated from acurrent supply circuit 14 and generates an electromagnetic field, whichis utilized to mechanically form and/or weld portions of a tube and acorresponding fitting to form a fluid joint. The current supply circuit14 may include a capacitor bank 16 and a power source 18, as shown. Acontroller 20 is coupled to the capacitor bank 16, via transmissionlines and buses (not shown), and controls charge and discharge thereofvia the power source 18. The induction coil 12 may be coupled to aconcentrator 22 and to an electromagnetic forming insert 24 for focusingelectrical current within the induction coil 12. Features of the insert24 are described in greater detail below. The controller 20 prior toforming a fluid joint may select from various inserts 26, nests 28, andmandrels 30, within a storage unit 32, that correspond to a particulartube and fitting combination, as will become more apparent in view ofthe following description. The selected insert and nest are fastenedwithin a fixed electromagnetic forming structure 34 prior toelectromagnetic forming of a tube and/or a fitting.

The concentrator 22 and electromagnetic forming insert 24 are used toadapt a compression coil, such as the induction coil 12, to a smallerdiameter workpiece, having a smaller diameter than the induction coil.The concentrator 22 and the insert 24 concentrate the magneticallyexerted pressure to a specific location on a tube and/or a fitting. Whenthe capacitor bank 16 is discharged through the induction coil 12, theinduced current in the magnetic field produces a magnetic pressure onthe conductive tube and/or fitting. The amount of discharged powerproduces a sufficient amount of magnetic compressive or expansivepressure to conform and deform the tube and/or fitting.

The magnetic forming system 10 may include an interchanging device 36that is coupled to the controller 20 and to the power source 18. Theinserts 26, nests 28, and mandrels 30 may be manually selected orselected via the interchanging device 36 by the controller 20 for aparticular fluid joint. The interchanging device 36 may be of varioustypes and styles as known in the art for the selection, replacement,insertion, and coupling of the inserts 26, nests 28, and mandrels 30, aswell as various tubes and fittings within the magnetic forming system10. The interchanging device 36 may be in the form of an automatedmanufacturing system and have rails and motors for the selecting,rotating, coupling, inserting, sliding, and removing of inserts, nests,and mandrels during fluid joint production. The interchanging device 36may be robotic in nature and have mechanical moving arms.

The controller 20 may be in the form of a control circuit and haveswitching devices for the control of the power settings utilized. Thecontroller 20 may be microprocessor based such as a computer having acentral processing unit, memory (RAM and/or ROM), and associated inputand output buses. The controller 20 may be an application-specificintegrated circuit or may be formed of other logic devices known in theart. The controller 20 may be a portion of a central main control unit,a control circuit, combined into a single integrated controller, or maybe a stand-alone controller as shown.

The inserts 26 are generally toroidally shaped and include constraininginserts 38 and electromagnetic forming inserts 40. The constraininginserts 38 prevent outward expansion of the fittings and the tubes beingformed. The electromagnetic forming inserts 40 are utilized to generateelectromagnetic fields to cause the deformation of a tube and/or fittingto form a fluid joint. The electromagnetic inserts 40 may also constrainor limit outward expansion of a tube and/or fitting.

Note that the sizes, materials, and current outputs of the components ofthe induction coil 12 and of the current supply circuit 14 are differentdepending upon whether electromagnetic mechanical forming ormetallurgical welding is performed. For example, in performingmetallurgical welding the size and capacity of the capacitor bank andthe size of the induction coil are generally larger than those used toperform electromagnetic mechanical forming, due to the larger amount ofenergy exerted in metallurgical welding. An exerted energy example isprovided below with respect to the embodiment of FIGS. 2A and 2B.

The below described embodiments of FIGS. 2A-5B, are sample embodimentsthat may be utilized in the electromagnetic forming of the walls of afitting and of a tube to form a fluid tight joint.

Referring now to FIGS. 2A and 2B, a cross-sectional side view of aninsert/nest assembly 50 that may be incorporated into the fixedstructure 34 and a front half cross-sectional view of the insert/nestassembly 50 are shown in accordance with an embodiment of the presentinvention. The insert/nest assembly 50 is attached to the fixedstructure 34 via a fixed base 52 and a fixed receptacle 54. The base 52is coupled within the fixed structure 34 and the receptacle 54 iscoupled within the base 52. The base 52 and the receptacle 54 may be ofsimilar size and shape as the induction coils and concentrators of theembodiments of FIGS. 3A-5B. A removable split constraining insert 56 isaxially clamped within the receptacle 54 and is coupled within aremovable split nest 58. The nest 58 holds a ferrule or fitting 60 andtube conduit 62 therein for magnetic forming thereof. An induction coil64 resides within the tube 62. The induction coil 64 is used to generatean electromagnetic field to expand and deform the end 66 of the tube 62,such that a mechanically formed or metallurgically welded joint may beformed between the fitting 60 and the end 66.

An assembly clearance gap G₁ resides between the tube 62 and theinduction coil 64. A fly distance gap G₂ resides between the fitting 60and the tube 62, which allows for the acceleration of the material inthe end 66 to be accelerated towards the fitting 60. In one sampleembodiment the gaps G₁ and G₂ are approximately 0.05 inches in width.

The induction coil 64 has one or more coils 68 and may be of varioussizes, shapes, and strengths and may be formed of various materials. Formechanical deformation of the end 66, the induction coil 64 may generatea current pulse having approximately 2 kJ of energy. Of course, othercurrent pulses having other amounts of energy may be utilized dependingupon the materials utilized, the sizes of the fittings and the tubesutilized, and other known parameters. For metallurgical welding of thefitting 60 with the end 66, the induction coil 64 may generate an energypulse having approximately between 50-100 kJ. In one metallurgicalwelding embodiment of the present invention, the energy pulse isapproximately 80 kJ. The induction coil 64 may have a handle portion 70with a first step 72 and a second step 74, which may abut the nest 58and the fitting 60, respectively.

The receptacle 54 and the insert 56 may be formed of various materialsthat allow for the outward constraining of the fitting 60 and the tube62. The receptacle 54 and the insert 56 may be formed of stainless steeland are used to prevent or limit the outward expansion of the fitting 60and the tube 62. The receptacle 54 includes a tapered inner surface 76that correspond with a tapered outer surface 78 of the insert 56, whichallow for the clamping and proper securing of the insert 56 within thereceptacle 54. Although the insert 60 is shown as having a taperedsurface 76, which is axially clamped within the receptacle 54, theinsert 60 may be coupled to the receptacle 54 utilizing other knowncoupling techniques. The axial clamping force applied to the insert 56is represented by arrows 80.

The nest 58 may be of various sizes, shapes, and styles, and may beformed of various non-metallic materials. In one embodiment, the nest 58is formed of plastic. The nest 58 holds the fitting 60 and the tube 62in alignment. The nest 58 also holds the induction coil 64 in place forproper alignment with the fitting 60 and the tube 62.

The insert 56 also includes tapered sides 82 and 84 that correspond withan insert-angled channel 86 of the nest 58. The tapered sides 82 and 84converge towards a centerline 88 of the nest 58. As the insert 56 isclamped into the receptacle 54, inward force is exerted on the walls 90of the nest 58, which holds the upper half 92 and the lower half 94 ofthe nest 58 in place relative to each other. The left side 87 and theright side 89 of the nest 58 may be coupled to each other via fastenersextending therethrough in a circular pattern or via some other techniqueknown in the art. The receptacle 54 and the insert 56 may be integrallyformed as a single unit.

The fitting 60 and the tube 62 may be formed of various metallicmaterials, such as aluminum, stainless steel, and titanium. The fitting60 includes grooves 100, in a tube inlay section 101, in which the wall102 of the tube 62 is deformed therein. This deformation into thegrooves 100 provides a non-sealant based fluid tight seal. Although anon-sealant based fluid tight seal may be formed as suggested, sealantsknown in the art may be utilized, for example, an 0-ring or adhesive maybe utilized between the fitting 60 and the tube 62. The tube end 66 mayabut the fitting 60 at the inner step or tube-butting edge 104 of thefitting 60. The tube 62 is shown having a nut 106 for coupling to aunion. The threads 108 of the nut 106 may reside on an internal surface110 of the nut 106, as shown, or may reside on an external surface, asshown in FIG. 4A.

The insert 56 and nest 58 are split to provide ease in set-up anddisassembling of the insert/nest assembly 50. The insert 56 includes aninsert upper half 112 and an insert lower half 114. The nest 58, asstated above, includes the nest upper half 92 and the nest lower half94. A gap G₃ resides between the upper halves 92 and 112 and the lowerhalves 94 and 114 for magnetic reaction.

Referring now to FIGS. 3A and 3B, a cross-sectional side view of ainsert/nest assembly 130 that may be incorporated into the fixedstructure 34 and a front half cross-sectional view of the insert/nestassembly 130 are shown in accordance with another embodiment of thepresent invention. The insert/nest assembly 130 is coupled within apermanent or fixed concentrator 132, which in turn is coupled within apermanent or fixed induction coil 134. The insert/nest assembly 130includes an electromagnetic forming insert 136 that resides within theconcentrator 132. An inward constraining mandrel 138 resides within thefitting 140 and the tube 142.

The gap G₃′ resides between the upper halves 157 and 164 and the lowerhalves 159 and 166. An assembly clearance gap G₄ resides between theinsert 136 and the tube end 143. A fly distance gap G₅ resides betweenthe fitting 140 and the tube 142, which allows for the material in theexpanded portion 144 to be accelerated towards the tube 142.

In operation, current within the induction coil 134 is focused by theconcentrator 132 and the insert 136 to generate an electromagneticfield, which is imposed on the fitting 140. The expanded portion 144 ofthe exterior wall 146 of the fitting 140 is compressed and acceleratedtowards the tube 142. The mandrel 138 limits the inward displacement ofthe fitting and the tube 142.

The concentrator 132 and the insert 136 may be formed of berylliumcopper BeCu or the like. The concentrator 132 also has a tapered innersurface 148 that corresponds with a tapered outer surface 150 of theinsert 136. The tapered surfaces 148 and 150 and the couplingtherebetween allow for the clamping and the proper securing of theinsert 136 within the concentrator 132. The tapered surfaces 148 and 150assure a solid contact between the concentrator 132 and the insert 136,such that there is no arcing therebetween and also provides for properoperation of the associated magnetic forming system. The concentrator132 and the insert 136 may be integrally formed as a single unit.

Like the insert 56, the insert 136 also includes tapered sides 152 and154 that correspond with an insert-angled channel 156 of the nest 158.The tapered sides 152 and 154 converge towards a centerline 160 of thenest 158. As the insert 136 is clamped into the concentrator 132, inwardforce is exerted on the walls 162 of the nest 158, which holds the upperand lower halves 164 and 166 of the nest 158 in place relative to eachother. The insert 136 includes an insert upper half 157 and an insertlower half 159.

The mandrel 138 has a handle portion 170 and an insert portion 172 witha step 174 therebetween. The insert portion 172 may be slightly tapered,although not shown, and is inserted within the fitting 140 and the tube142. The outer edges 176 of the insert portion 172, when tapered, aretapered inward towards the centerline 160 away from the handle portion170. The mandrel 138 may abut the nest 158 or the fitting 140 via thefirst step 178 or the second step 174, respectively. The mandrel 138, asan example, may be formed of stainless steel and plastic.

Referring now to FIGS. 4A and 4B, a cross-sectional side view of ainsert/nest assembly 200 that may be incorporated into the fixedstructure 34 and a front half cross-sectional view of the insert/nestassembly 200 are shown in accordance with still another embodiment ofthe present invention. The configuration of the insert/nest assembly 200is similar to that of the insert/nest assembly 130. However, in theexample embodiment of FIGS. 4A and 4B a tube 202 having an expanded end204 is compressed onto a fitting 206, as opposed to a fitting beingcompressed onto a tube. Fitting features are described with respect tothe embodiments of FIGS. 7-9. Thus, the electromagnetic forming insert208 has a different shape than the insert 136 to accommodate for thisdifference in the tube/fitting relationship.

An assembly clearance gap G₆ resides between the tube 202 and the insert208. A fly distance gap G₇ resides between the tube 202 and the fitting206, respectively, which allows for the material in the expanded end 204to be accelerated towards the fitting 206.

Note that the nut 210 on the tube 202 has threads 212 on an exteriorside 214 as opposed to an interior side, as with the nut 106. There isno correlation between the overlap relationship of the fitting 206 andthe tube 202 and the location of the threads 212. The threads 212 areshown on the exterior side 214 to illustrate another possible embodimentand another example as to the different internal shape of a nest. Thenest 216 is shaped to accommodate the insert 208 and the nut 210.

Referring now to FIG. 5, a side cut-away view of a tube/fitting coupling240 is shown, incorporating a tube/fitting fluid joint 242 formed usingone of the insert/nest assemblies 50 and 130. The fluid joint 242 is anon-sealant based fluid tight seal, as well as other fluid joints hereindescribed. The tube/fitting coupling 240 includes a first tube 244having a union 246 residing thereon and a second tube 248 having a nut250. In connecting the first tube 244 to the second tube 248 the nut 250is threaded onto the union 246. The tip 252 of the union 246 is pressedinto the ferrule 254 due to the coupling between the nut 250 and theferrule 254 and the threading of the nut 250 onto the union 246. The nut250 includes a ferrule-chamfered surface 256 that corresponds with amiddle tapered exterior surface 258 of the ferrule 254. As the nut 250is threaded onto the union 246 the nut 250 pulls the union 246 into theferrule 254.

The union 246 may include grooves 260 on an interior surface 262. Afirst end 264 of the first tube 244 may be expanded and formed into thegrooves 260 using a magnetic forming or magnetic welding process asdescribed herein. The ferrule 254 resides between the nut 250 and theunion 246 and is coupled to the second tube 248 via a magnetic formingor magnetic welding process of the present invention, such as thatdescribed in the embodiments of FIGS. 2A-3B.

The ferrule 254 includes a union chamfered surface 265 in which thetapered tip 252 resides when coupled to the ferrule 254. The ferrule 254also includes multiple grooves 266 on an interior side 268 for formingof the second tube 248 therein.

Referring now to FIGS. 6A and 6B, a half-side cross-sectional view of atube/fitting coupling 270 is shown prior and subsequent to magneticformation using the assembly of FIG. 4A, along with a side cut-away viewof the tube/fitting coupling 270 subsequent to magnetic formation.

The tube/fitting coupling 270 includes a first tube 292 and a secondtube 274. The second tube 274 is coupled to a fitting 272 via a fluidtight joint 276 therebetween. The fitting 272 includes multiple grooves278 that are located on an exterior side 280 of the fitting 272 in atube overlap region 282. The tube 274 has an end portion 284 thatoverlaps the fitting 272. The end portion 284 is expanded prior to beingslid over the overlap region 282. Fly distance gaps G₈ and G₉ existbetween the overlap region 282 and the end portion 284. The fly distancegaps G₈ and G₉ exist between the grooves 278 and the end portion 284 andbetween the end portion 284 and the ribs 286, respectively.

In FIG. 6A, the end portion 284 is shown in a first position 288,representing the end portion 284 prior to magnetic forming, and in asecond position 290, representing the end portion 284 subsequent tomagnetic forming. During magnetic forming the end portion 284 is formedinto the grooves 278. The bent sections of the end portion 284 may bereferred to as electromagnetic field formed wall deformations. Threesuch sections 291 are shown.

In FIG. 6B, the tube/fitting coupling 270 is shown illustrating theunion coupling between the first tube 292 and the second tube 274. Thetube/fitting coupling 270 includes the first tube 292 and the union 294,which are similar to the first tube 244 and the union 246. The firsttube 292 and the union 294 are coupled to the second tube 274 and to theferrule 272.

Referring now to FIG. 6C, a side cut-away view of a tube/fittingcoupling 295 subsequent to metallurgical formation. The tube/fittingcoupling 295 includes a tube/fitting mesh 296 that is a metallurgicallyformed fluid circuit joint, which is in the form of a shared wallsection between a tube 297 and a ferrule 298. The tube/fitting mesh 296includes materials from wall portions of the tube 297 and the ferrule298.

Although metallurgical welding may be applied to any of theconfigurations of FIGS. 2A-4B, since the walls of the fitting and of thetube are metallurgically combined, a fitting and a tube that do notcontain any grooves may be utilized in the metallurgical welding processto form a fluid tight joint.

The embodiments of FIGS. 2A-4B may be applied to various fluidapplications, including low-pressure and high-pressure fluidapplications, to form the tube/fitting joints of FIGS. 5-6C. Thetube/fitting joints of FIGS. 5-6C when containing thin-walled tubesand/or fittings are capable of withstanding internal fluid pressures ofapproximately equal to or less than 2500 psi and thus have a fluidpressure rating as such. Of course, thick-walled tubes and/or fittingsmay be utilized for high-pressure applications. An example of athin-walled tube is one in which the thickness of the tube wall isapproximately less than 0.1 multiplied by the average radius of thetube.

Referring now to FIG. 7, a cross-sectional side view of a samplefluid-carrying ferrule 300 in accordance with an embodiment of thepresent invention is shown. The fluid-carrying ferrule 300 includes awall 302 having a fluid-union coupling region 304 and a tube overlapregion 306. A tube end, not shown, may reside over the overlap region306 and abut the step 308 of the wall 302.

The overlap region 306 includes multiple grooves 310. Although twogrooves are shown having a particular shape and size, any number ofgrooves, having various sizes and shapes may be utilized, depending uponthe application. Each groove 310 provides an additional fluid tighttransition for additional leak prevention.

In the embodiment shown, the overlap region 306 includes a first groove312 and a second groove 314. The first groove 312 is slightly wider thanthe second groove 314. There is approximately equal distance between thestep 308 and the first groove 312 as between the first groove 312 andthe second groove 314. The widths W₁ and W₂ of the grooves 310 may beapproximately equal to the separation distances D₁ and D₂ between thestep 308 and the grooves 310.

The ferrule 300 also includes a chamfered inner surface 316 for couplingto a union, such as unions 246 and 294. The ferrule 300 furtherincludes, within the overlap region 306 a break edge 318, which allowsfor easy insertion into a tubular conduit.

Referring now to FIGS. 8 and 9, cross-sectional side views of samplehydraulic fluid carrying ferrules 330 and 332 are shown in accordancewith an embodiment of the present invention. The hydraulic ferrules 330and 332 include walls 334 and 336 having hydraulic union couplingregions 338 and 340 and tube overlap regions 342 and 344.

The hydraulic-coupling regions 338 and 340 are different than that ofthe air-coupling region 304 to accommodate for the differentapplication. The hydraulic-coupling regions 338 and 340 may include astandard wall section 350, steps 352, and arched sections 354. The steps352 include radius edges 359 that are associated with an end of atubular conduit (not shown).

The tube overlap regions 342 and 344 are similar to the tube overlapregion 306. The tube overlap regions 342 and 344 may or may not have abreak edge.

In the methods of FIGS. 10-12, the material compositions of the tubesand the fittings utilized can affect the ability of the tubes and or thefittings to be deformed. As an example, when it is desired for a fittingto be deformed as opposed to a tube, the material composition of thefitting may be adjusted and/or have less tensile strength than that ofthe tube to allow for such deformation. The thickness of the tube andfitting walls may also be adjusted to provide various degrees of tensilestrength. In addition, the electromagnetic current pulses utilized mayalso be adjusted to provide the desired deformation in the tube and thefitting.

Referring now to FIG. 10, a first sample method of magnetically forminga fluid joint in accordance with an embodiment of the present inventionis shown.

In step 502, the current tube is inserted into the current fitting. Thetube may be inserted into the fitting manually or through use of theinterchanging device 36. In step 506, the induction coil is insertedinto the current tube.

In step 508, inserting the current tube, the current fitting, and theinduction coil into a nest. The current tube, the current fitting, andthe induction coil are placed on a first half of a selected nest, suchas the nest half 92. The nest may be selected from the nests 28. Thesecond half of the nest, such as the nest half 94, is placed over thefirst half covering the fitting, the tube, and the induction coil.

In step 510, an insert, such as one of the constraining inserts 38 orthe constraining insert 56, is attached and/or inserted into the nest.

In step 512, the nest and the insert are clamped into a fixedreceptacle, such as the receptacle 54. The insert is press fitted intothe receptacle using techniques known in the art.

In step 514, a controller, such as the controller 20, via a capacitorbank and the induction coil generates an electromagnetic field. Anelectromagnetic current is discharged from the capacitor bank into theinduction coil in response to a current pulse signal generated from thecontroller 20.

In step 516, the induction coil in generating the electromagnetic fieldimposes the electromagnetic field upon the tube. The electromagneticfield accelerates the end of the tube toward the fitting, therebyexpanding the end of the tube within the fitting and deforming the endinto the grooves, such as the grooves 100, of the fitting. The flydistance gap, such as the gap G₂, between the tube and the inductioncoil and between the tube and the fitting allow for the acceleration ofthe tube end. The expansion and deformation of the tube end against thefitting forms a pressure tight fluid joint.

Electrical current from the capacitor bank is passed through theinduction coil, which generates an intense electromagnetic field andcreates high magnitude eddy currents in the tube end. The opposingmagnetic fields that are directly generated by the induction coil andthat are generated by the eddy currents accelerate the tube end towardsthe fitting. When electromagnetic mechanical forming is performed thetube end is deformed into the grooves of the fitting. Whenelectromagnetic welding is performed the tube end is metallurgicallywelded with the fitting.

A high current pulse of short duration, approximately between about 10and 100 microseconds, is introduced to the coils of the induction coil,which generates the electromagnetic field to instantaneously deform thetube radially outward towards the insert, resulting in the crimping ormetallurgical welding of the tube to the fitting to form the fluidjoint. The pulse is strong enough to induce magnetic forces above theyield strength of the material in the tube.

In step 518, the insert and the receptacle, during electromagneticforming of the tube, constrain or limit the expansion of the tube andthe fitting. Steps 514-518 are substantially performed simultaneously.

In step 520, upon completion of steps 514-518 the current nest isremoved from the receptacle containing the fluid joint. In step 522, thefluid joint is removed from the current nest. The first half and thesecond half of the current nest are separated to allow for the removalof the fluid joint.

In step 524, it is determined whether the current setup andconfiguration of the current tube and the current fitting is to bereused or replaced. The controller may determine whether to form anothertube/fitting coupling using the current insert and nest arrangement orto select a replacement insert and nest. The replacement insert and nestmay have different internal dimensions as compared with the currentinsert and nest and may be selected from the constraining inserts 38 andthe nests 28. The different internal dimensions may correspond to atube/fitting coupling of different size, to a tube/fitting couplinghaving a different tube/fitting configuration, to a tube/fittingcoupling formed using a different electromagnetic forming orelectromagnetic welding technique, or to other known tube/fittingrelated differences known in the art. Steps 520-524 may be performed viathe interchanging mechanism 36. Upon selection of a second orreplacement tube, a second or replacement fitting, a replacement insert,and a replacement nest, the controller 20 returns to step 502.

Referring now to FIG. 11, a second sample method of magnetically forminga fluid joint in accordance with another embodiment of the presentinvention is shown.

In step 550, a tube insert section or portion of a current fitting, suchas the portion 144, may be expanded also via an end-forming device ororiginally machined with the tapered shape. In step 552, a tube end of acurrent tube, such as the tube end 143, is inserted into the fitting. Instep 554, a temporary mandrel is selected, such as the mandrel 176, andis inserted into the tube and the fitting. The mandrel is inserted intothe tube to prevent excessive tube-wall collapse.

In step 556, the tube, the fitting, and the mandrel are inserted into acurrent nest, such as the nest 166. The tube, the fitting, and themandrel are placed on a first half of the nest. The second half of thenest is placed over the first half covering the fitting, the tube, andthe mandrel. In step 558, an insert, such as one of the electromagneticforming inserts 40 or the electromagnetic forming insert 136, isattached and/or inserted into the nest.

In step 560, the nest and the insert are clamped into a fixedconcentrator, such as the concentrator 132. The insert is press fittedinto the concentrator using techniques known in the art.

In step 562, the controller 20, via a capacitor bank and an inductioncoil, such as the induction coil 134, generates a first stageelectromagnetic current that is passed into the concentrator viacoupling between the concentrator and the induction coil. Anelectromagnetic current is discharged from the capacitor bank into theinduction coil, which is then passed into the concentrator. In step 564,a field concentrator focuses the first stage electromagnetic current toform a second stage electromagnetic current, which is passed into theinsert via the coupling between the concentrator and the insert. In step566, the insert focuses the second stage electromagnetic current andforms an electromagnetic field.

In step 568, the electromagnetic field is imposed upon the exterior ofthe fitting and accelerates and compresses the tube insert section ontothe tube. In accelerating and compressing the fitting onto the tube, thetube end is deformed into the grooves of the fitting. The fly distancegap, between the tube and the fitting and between the insert and thetube, such as the gap G₅, allows for the acceleration of the tube insertsection of the fitting. The compression of the fitting and thedeformation of the tube form a fluid joint. In step 570, the mandrelconstrains or limits the compression of the fitting and the tube duringelectromagnetic formation. Steps 562-570 are substantially performedsimultaneously.

In step 572, upon completion of steps 562-570 the current nest isremoved from the concentrator containing the fluid joint. In step 574,the fluid joint is removed from the current nest. The first half and thesecond half of the current nest are separated to allow for the removalof the fluid joint.

In step 576, it is determined whether the current setup andconfiguration of the current tube and the current fitting is to bereused or replaced, similar to step 524 above. The controller maydetermine whether to form another tube/fitting coupling using thecurrent insert and nest arrangement or to select a replacement insertand nest. Steps 572-576 may be performed via the interchangingmechanism. Upon selection of a second or replacement tube, a second orreplacement fitting, a replacement insert, and a replacement nest, thecontroller returns to step 550.

Referring now to FIG. 12, a third sample method of magnetically forminga fluid joint in accordance with still another embodiment of the presentinvention is shown.

In step 600, a current tube end, such as the tube end 204, is expandedusing an end-forming device. In step 602, a current fitting, such as thefitting 206 or the fitting 272, is inserted into the tube end. In step604, a mandrel, such as the mandrel 138, is inserted into the tube andthe fitting.

In step 606, the tube, the fitting, and the mandrel are inserted into acurrent nest, such as the nest 216. The tube, the fitting, and themandrel are placed on a first half of the nest. The second half of thenest is placed over the first half covering the fitting, the tube, andthe mandrel.

In step 608, an insert, such as one of the electromagnetic forminginserts 40 or the electromagnetic forming insert 208, is attached and/orinserted into the nest. In step 610, the nest and the insert are clampedinto a fixed concentrator, such as the concentrator 132. The insert ispress fitted into the concentrator using techniques known in the art.

In step 612, the controller 20, via the capacitor bank and the inductioncoil, such as the induction coil 134, generates a first stageelectromagnetic current that is passed into the concentrator viacoupling between the concentrator and the induction coil. Anelectromagnetic current is discharged from the capacitor bank into theinduction coil, which is then passed into the concentrator. In step 614,the field concentrator focuses the first stage electromagnetic currentto form a second stage electromagnetic current, which is passed into theinsert via the coupling between the concentrator and the insert. In step616, the insert focuses the second stage electromagnetic current andforms an electromagnetic field.

In step 618, the electromagnetic field is imposed upon the exterior ofthe tube and accelerates and compresses the tube end onto the fitting,similar to step 568 above. In accelerating and compressing the tube ontothe fitting, the tube end is deformed into the grooves of the fitting.The fly distance gap between the tube and the fitting and between theinsert and the tube, such as the gap G₇, allows for the acceleration ofthe tube end. The compression and deformation of the tube end forms afluid joint. In step 620, the mandrel constrains or limits thecompression of the fitting and the tube during electromagneticformation. Steps 612-620 are substantially performed simultaneously.

In step 622, upon completion of steps 612-620 the current nest isremoved from the concentrator containing the fluid joint. In step 624,the fluid joint is removed from the current nest. The first half and thesecond half of the current nest are separated to allow for the removalof the fluid joint.

In step 626, it is determined whether the current setup andconfiguration of the current tube and the current fitting is to bereused or replaced, similar to steps 524 and 576 above. The controllermay determine whether to form another tube/fitting coupling using thecurrent insert and nest arrangement or to select a replacement insertand nest. Steps 612-626 may be performed via the interchangingmechanism. Upon selection of a second or replacement tube, a second orreplacement fitting, a replacement insert, and a replacement nest, thecontroller returns to step 600.

Note that the above methods may be performed without the use oflubrication, which minimizes steps involved and can eliminate the needfor cleaning of the fittings, tubes, and fluid tight joints.

The above-described steps in the methods of FIGS. 10-12 are meant to beillustrative examples; the steps may be performed sequentially,synchronously, simultaneously, or in a different order depending uponthe application.

The present invention provides fluid tight leak joints with reducedscrap rate. Further, because the insert/nest assemblies are quickly andeasily inserted and removed from a fixed structure, a large quantity oftubular joints may be quickly formed. The above stated reduces costsassociated with manufacturing down times.

The present invention reduces manufacturing processing steps as comparedto conventional welding and roller swaging or elastomeric processes. Thepresent invention also reduces inspection process steps, cost ofproduction, and provides a highly reproducible manufacturing process tomaintain consistent quality.

While the invention has been described in connection with one or moreembodiments, it is to be understood that the specific mechanisms andtechniques which have been described are merely illustrative of theprinciples of the invention, numerous modifications may be made to themethods and apparatus described without departing from the spirit andscope of the invention as defined by the appended claims.

1. A magnetic forming system for creating a fluid circuit joint betweena tube and a fitting comprising: an induction coil forming a first stageelectromagnetic current; a field concentrator electrically coupled tosaid induction coil and focusing said first stage electromagneticcurrent to form a second stage electromagnetic current; and an insertelectrically coupled to said field concentrator and focusing said secondstage electromagnetic current to form an electromagnetic field, saidelectromagnetic field forming the fluid circuit joint.
 2. A system as inclaim 1 wherein said induction coil comprises an induction coil innerperimeter, said field concentrator residing within said induction coilinner perimeter.
 3. A system as in claim 1 wherein said fieldconcentrator comprises a field concentrator inner perimeter, said insertresiding within said field concentrator inner perimeter.
 4. A system asin claim 1 wherein said field concentrator comprises a fieldconcentrator inner perimeter that is tapered and said insert comprisesan insert outer perimeter that is tapered, said field concentrator innerperimeter and said insert outer perimeter forming an electricallytapered connection therebetween.
 5. A system as in claim 1 wherein saidelectrical coupling between said field concentrator and said insert isgap free.
 6. A system as in claim 1 further comprising: a controllergenerating a current pulse signal; and a current supply circuitgenerating a current pulse in response to said current pulse signal;said induction coil generating said electromagnetic field in response tosaid current pulse.
 7. A system as in claim 6 wherein said insertelectromagnetically forms the tube onto the fitting.
 8. A system as inclaim 6 wherein said insert electromagnetically forms the fitting ontothe tube.
 9. A system as in claim 1 wherein said insert is cylindricallyshaped and comprises: a first insert half and a second insert half thatis separable from said first half.
 10. A system as in claim 9 furthercomprising: a nest containing the tube and the fitting, said nestcomprising: a first nest half coupled to said first insert half and asecond nest half coupled to said second insert half.
 11. A system as inclaim 9 wherein said insert comprises a gap between said first half andsaid second half when fully seated within said field concentrator.
 12. Asystem as in claim 11 wherein said insert comprises an insulating memberresiding within said gap.
 13. A system as in claim 1 further comprisinga nest coupled to said insert and at least partially containing the tubeand the ferrule.
 14. A system as in claim 13 wherein said nest containsa mandrel that limits the compression of the tube and the ferrule.
 15. Asystem as in claim 1 further comprising a mandrel inserted within andlimiting compression of the tube and the fitting.
 16. A magnetic formingsystem for creating a fluid circuit joint comprising: a electromagneticcoil forming a first stage electromagnetic current; a fixednon-removable magnetic field concentrator coupled to saidelectromagnetic coil and focusing said electromagnetic current to form asecond stage electromagnetic current; and a plurality of interchangeableremovable inserts each of which having an internal configuration for anassociated tube and fitting, each of said plurality of interchangeableremovable inserts is electrically coupled to said field concentratorwhen selected and focuses said second stage electromagnetic current toform an electromagnetic field, said electromagnetic field forming thefluid circuit joint between said tube and said fitting.
 17. A system asin claim 16 further comprising an interchanging mechanism replacing afirst insert with a replacement insert selected from said plurality ofinterchangeable removable inserts.
 18. A system as in claim 16 furthercomprising a plurality of nests having a plurality of tube/fittingconfigurations, each of said nests selectable to contain said tube andsaid fitting.
 19. A system as in claim 18 farther comprising aninterchanging mechanism replacing a first nest with a replacement nestselected from said plurality of nests.